Making DVDs with 352x240 size source mpgs - how?

ken c wrote on 1/8/2005, 2:27 AM
Hi - quick question: I want to compress down some of the 2-3 day seminar instructional DVD courses I've bought, some of them are 8+ DVDs in length.

I've used womble to rescale the vobs down to 352 x 240 size format, cutting the file size for each by 75%. That part's fine. I've got a bunch of correctly resized mpgs I now need to make DVDs out of...

Now how, in DVDA2, can I make new DVDs, say 2 DVDs out of the original 8?

The image quality of course is 'stretched', poor, but that's ok, my goal for these is to have either small middle of screen 352x240, or preferably, just 'stretched' 352 x 240 (into the 740x480 size) video format.

Trying to import the mpgs into DVDA2, I'd have to use a bit rate way down at 1 mps, far too lossy, even when making the project setting at 352x240, to get them in the project.... I'm a bit confused.. eg it says a 400 meg mpg becomes 1.9 gigs, in effect 're-expanding' the source back to 740x480 format, which isn't what I want, at 5-8 Mps .. I just want to create lower-quality vcd-type dvds, so I can pack all the 8 dvds into 2, at 352 x 240 resolution.

does that make sense? hopefully I've explained it.. any tips on what I can do in DVDA2 to compress them correctly? (maybe I should put this in the dvda forum?)

So, what I'm asking is, how can I get 400 megabyte 352x240 mpgs included in my DVDA2 project (whether I define the project to be vcd format same as source, or dvd size, it still shows 4x mps) at 5 mps so that they're still about 400 megs each?

thanks,

ken

Comments

Chienworks wrote on 1/8/2005, 6:10 AM
It's all about the bitrate. Frame size makes almost no difference at all. If you encode at 5Mbps you'll get the same size .mpg file whether your frame size is 160x120 or 1920x1080. If you want smaller output files then you must use a lower bitrate no matter what your frame size is.

Output file size = bitrate x length. There are no other (significant) variables in that equation.
JSWTS wrote on 1/8/2005, 6:18 AM
You won't be able to do what you are posting with DVD-A 1 or 2. 352x240 (mpeg1) and 352x480(half D1) are accepted frame sizes and formats under the dvd spec, but are not supported by DVD-A (at least at this time). There are other apps that do support the other frame sizes and accomplish what you are trying to do. Using full frame mpeg2 for recompressing your original footage will look pretty bad.

Jim
bStro wrote on 1/8/2005, 8:27 AM
Just to clarify, 'cause I'm not sure if Jim is saying that DVDA doesn't support 352x240 MPEG1 or if he's saying it doesn't support 352X240 of any kind (including MPEG2):

DVDA 2.0 does support 352x240 MPEG2. Go to File -> Properties and look through the options listed for Project video format -- NTSC 352x240 is there, as are 352x480 and 704x480. I think the hurdle for the original poster is that he's trying to use too low a bitrate, and DVDA is saying "Oh, no you don't," and decides to re-encode the file.

Edit: Oh, and if the original files are MPEG1, DVDA will make them MPEG2.

Rob
JSWTS wrote on 1/8/2005, 8:59 AM
My bad, you are right, DVD-A2 does support a variety of mpeg2 formats. I can't tell from the original post what the duration of the original disc content was--based on that I would set my parameters for re-encoding to a smaller frame size and lower bitrate. If the poster needs to put > 4 1/2 hours per disc, then I would recommend mpeg1which one can get roughly 7 hours per disc (but DVD-A doesn't support it--as best I can tell). If it would be around 3-4 hours per disc, then I would use half D1 (352x480). 352x240 for mpeg 2 (although accepted by DVD-A2) is a very unusual frame size. The most common are full d1, half d1, mpeg1, and broadcast d1. I personally have never seen 352x240 mpeg2 used, but as posted, it is supported by DVD-A2. If the file size jumps when trying to output it's obvious there is something about the file that DVD-A2 considers non-compliant and is re-encoding the file again. I also agree that the bitrate chosen is way too low for mpeg2, in fact, it's pushing it for even mpeg1 at 352x240.

The original poster mentions he would like to just have vcd quality files with all 8 dvd's 'packed' on to a couple of discs. VCD would be mpeg1 (and is supported by the dvd specs, but not DVD-A), and that might be a part of the issue as well.

Jim
ken c wrote on 1/8/2005, 12:23 PM
thanks all - very helpful... didn't know re: bitrate part of equation is fixed etc.. appreciate it..

and true, I'd be happy w/mpg1 for these (I keep them running in the background on tv, seminar videos, so image quality not as critical)..

ken